There is known a conventional load detecting apparatus for detecting load applied to a support for a load sensor, such as a bed, a mat, a seat, etc., thereby determining presence/absence of a human, an animal or a physical object. There has been also proposed an apparatus adapted for detecting micro vibrations such as heartbeat, breathing of a human, in addition to such determination of presence/absence of a human, an animal or a physical object.
Patent Document 1 identified below describes an invention relating to such load detecting apparatus. In this load detecting apparatus, a support for supporting a human body includes a vibration detecting means having a vibration generating section and a vibration detecting section disposed adjacent the vibration generating section. This load detecting apparatus further includes a vibration characteristics calculating means and a load calculating means. The vibration characteristics calculating means calculates vibration characteristics of vibration propagated due to vibration of the vibration generating section, from an output signal from the vibration detecting section. Then, the load calculating means calculates load applied to the vibration detecting means, based on an output signal from this vibration characteristics calculating means. The apparatus still further includes a human body vibration extracting section for extracting vibration component due to the human body present on the support, from the output signal of the vibration detecting section. Examples of the vibration component extracted are vibration associated with heartbeat and breathing of the human body. Finally, a human body determining means is provided for determining presence/absence of a human body on the support, based on the output signals from the human body vibration extracting section and the load calculating section.    Patent Document: Japanese Patent Application “Kokai” No. 2000-230853 (see paragraphs 8-16, FIGS. 1-5 and FIGS. 8-10).